Photoproduction of a 100-μsec Isomer and its Tentative Assignment toHg201

The photoproduction of a 100±6-μsec isomer from a natural Hg target was studied as a function of bremsstrahlung energy by detecting the 533±7 keV gamma ray which dominates the decay. The isomer is produced mainly by a ($\gamma , n$) process which has an apparent threshold of 11.3±0.3 MeV and an integrated cross section of 33 MeV mb if the 30% isotope ${\mathrm{Hg}}^{202}$ is the parent. In the energy range from 9 to 12 MeV, the isomer is probably produced by a ($\gamma , {\gamma }^{\prime }$) process.